Microscopic analyzers are used for analyzing a micro-sized measurement area on a sample.
FIG. 1 shows one configuration example of an infrared microscope which is one type of the microscopic analyzer. In the infrared microscope, a sample 1 placed on a sample stage is illuminated with infrared light, and an emission of light from the illuminated area is detected with an infrared detector 9. There are two measurement methods in the infrared microscope. One method is to illuminate the sample 1 with the infrared light from the obverse side of the sample and detect the reflected light. The other method is to illuminate the sample from the reverse side of the sample 1 and detect the transmitted light.
The light emitted from the sample 1 is collected with a Cassegrain reflector 6 consisting of a concave mirror 6a with a through-hole formed at its center and a convex mirror 6b. The collected light falls onto the infrared detector 9 through a small opening (aperture 8) surrounded by a plurality of aperture plates. The aperture 8 is placed at a position which is conjugate to the sample 1 with respect to the Cassegrain reflector 6 (i.e. the position where the image of the sample 1 is formed). In a measurement, while checking the position on an image of the surface of the sample 1 taken with a camera 22, an operator drives the sample stage to locate the measurement target area at the center of the visual field of the infrared microscope. Subsequently, the operator adjusts the size of the aperture 8, and then rotates the aperture 8 to fit the visual field of the infrared microscope to the measurement target area.
The size of the aperture 8 is adjusted, for example, by opening or closing one pair of aperture plates which define the aperture width in one direction and another pair of aperture plates which define the aperture width in another direction that is perpendicular to the first direction. A feed screw (male screw) extending in the driving direction of the aperture plates is engaged with the threaded hole (female screw) formed in a drive block fixed to each aperture plate. A linear motion guide (translation bearing) determines the moving direction of the drive block while restricting the rotation of the same block. With such a mechanism, a rotation of the feed screw is converted into a linear motion of the drive block (and the aperture plate) Patent Literature 1 discloses an aperture-plate drive mechanism including an aperture-plate open-close mechanism for driving aperture plates and a rotation mechanism for rotating the aperture plates around an axis perpendicular to the aperture plates, in which each pair of the aperture plates (and drive blocks) facing each other across their open-close center are simultaneously driven in opposite directions (closer to or farther away from each other) by using, as a feed screw, a double-end screw having two helical threads proceeding in the opposite directions, with the threaded hole of one drive block engaged with each thread.